The organic aerosols of Titan

Khare, B. N.; Sagan, Carl; Thompson, W. R.; Arakawa, E. T.; Suits, Frank; Callcott, T. A.; Williams, M. W.; Shrader, S.; Willingham, T. O.; Nagy, Bartholomew

doi:10.1016/0273-1177(84)90545-3

Cited by 122 publications

(85 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We have found that tholin synthesized from a crude simulation of Jupiter is not pure poly-HCN but is a heteropolymer with a variety of moieties (13). The same conclusion is also drawn from the pyrolytic GC-MS results on this tholin as well as on Titan tholin (14,15,17); hundreds of pyrolytic products were detected in both tholins. But a diagnostic test is the comparison of laboratory optical constants of poly-HCN with optical constants derived from astronomical and spacecraft observations.…”

Section: Introductionsupporting

confidence: 74%

“…Laboratory experiments, done at Cornell University (14)(15)(16) and elsewhere, show that the gas-and solid-phase product molecules are diverse even in simulation experiments starting with only a few major precursor gases. We have found that tholin synthesized from a crude simulation of Jupiter is not pure poly-HCN but is a heteropolymer with a variety of moieties (13).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Optical properties of poly-HCN and their astronomical applications

Khare

Sagan²,

Thompson³

et al. 1994

Can. J. Chem.

View full text Add to dashboard Cite

Can. J. Chem. 72, 678 (1994). Matthews (1992) has proposed that HCN "polymer" is ubiquitous in the solar system. We apply vacuum deposition and spectroscopic techniques previously used on synthetic organic heteropolymers (tholins), kerogens, and meteoritic organic residues to the measurement of the optical constants of poly-HCN in the wavelength range 0.05-40 pm. These measurements allow quantitative comparison with spectrophotometry of organic-rich bodies in the outer solar system. In a specific test of Matthews' hypothesis, poly-HCN fails to match the optical constants of the haze of the Saturnian moon, Titan, in the visible and near-infrared, derived from astronomical observations and standard models of the Titan atmosphere. In contrast, a tholin produced from a simulated Titan atmosphere matches within the probable errors. Poly-HCN is much more N-rich than Titan tholin. [Traduit par la rCdaction]

show abstract

Section: Introductionsupporting

confidence: 74%

Section: Introductionmentioning

confidence: 99%

Optical properties of poly-HCN and their astronomical applications

Khare

Sagan²,

Thompson³

et al. 1994

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…In other words, different compounds may exhibit similar absorption properties. This has been demonstrated by Tran et al (2003), who show that various photolysis products exhibit very similar optical constants to those of the tholins of Khare et al (1984) …”

Section: Are Tholins Relevant Analogs?mentioning

confidence: 69%

“…Tholins have been proposed and are currently used as analogs of Titan's aerosols, reddish surfaces of outer satellites and TransNeptunian Objects, or interstellar organics (Khare et al 1984, Cruikshank et al 2005, de Bergh et al 2008. However, though the properties of some tholins match the optical constants of Titan's aerosols as well as other planetary organics, there is no evidence that their chemical structure is in fact similar.…”

Section: Introductionmentioning

confidence: 99%

Tholins and their relevance for astrophysical issues

Quirico¹,

Szopa

Cernogora

et al. 2008

Proc. IAU

View full text Add to dashboard Cite

Abstract.Tholins are polymeric hydrogenated carbon nitrides formed from N2 :CH4 mixtures exposed to electrical discharges. They are complex disordered solids, and their structural chemistry and formation processes are not yet fully understood. Tholins have been widely adopted as useful analogs of reddish organic solids associated with planetary bodies or in interstellar space (e.g., Titan's aerosols, reddish surfaces of outer objects, interstellar organics, etc.) for fitting astronomical observations. However, there has been little evidence to date that they in fact constitute pertinent model materials, i. e. with chemical structure/composition similar to those presumed to be present in planetary or interstellar organic solids. In this contribution, we first review recent advances made regarding the determination of composition and structure of tholins produced in the laboratory. They point to a high chemical selectivity in the range of functional groups present, the control of unsaturation by nitrogen, and the highly disordered character of the structures. In a second section, we discuss the relationship between chemistry and the optical properties of tholins, and we point out the lack of a unique relationship between the shape and strength of the visible absorption bands and the chemical composition or structure of the model tholins. The tholins exhibit similarities with HCN "polymers", that are suspected to be present in cometary refractory dust. This points to the existence of possible similar polymerisation processes, and it suggests they could also be used as analogs of N-rich cometary organics. Laboratory-based studies of cometary dust might offer new insights on the "chemical relevancy" of tholins, as combined micro-analytical techniques will allow direct comparison of chemical information between the materials produced. In a third section we present recent results pertaining to the search for such compounds in cometary grains (Stardust grains, interplanetary dust particles -IDPs). We show that some N-rich spots in stratospheric IDPs are rich in cyanide species, but no tholin-like compounds or polymeric HCN have been detected to date. 409at https://www.cambridge.org/core/terms. https://doi

show abstract

“…These tholins may be the very type of material delivered to Earth b y the consistent comet and asteroid bombardment that is known to have occurred during the infancy of the solar system. Experimentation has also shown that the hydrolysis of some tholins results in amino acid production (Khare et al 1983). …”

Section: Exobiological Analysis Of Organic Residuesmentioning

confidence: 99%

Function of Maximal Microvessel Density in Breast Tumor Metastasis

McLeskey¹

2000

View full text Add to dashboard Cite

Subject Terms Document Classification unclassified Classification of SF298 unclassified Classification of Abstract unclassified Limitation of Abstract unlimited Number of Pages 55 REPORT DOCUMENTATION PAGE Form Approved OMB No. 074-0188Public reporting burden for this collection of information is estimated to average 1 hour per response, including g the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. SUPPLEMENTARY NOTES 12a. DISTRIBUTION/AVAILABILITY STATEMENTThis document has been approved for public release; its distribution is UNLIMITED. 12b. DISTRIBUTION CODE ABSTRACT:An understanding of the formation of the larger molecules in the outer solar system, by radiation induced processing of more primitive constituents, has implications relating to the evolution of the solar system. Organic residues formed by cosmic ray irradiation on cosmic ices may also have some exobiological significance, directly relating to the process from which life began on Earth. Since Pluto is one of the most primitive, and well-preserved, bodies in the solar system, its surface chemistry is of particular relevance. This project was an attempt to correlate recent astronomical data with a radiation model for compound formation. Spectroscopic observations of Pluto suggest the presence of ethane, presumably caused by cosmic ray irradiation of methane trapped in solid nitrogen at the surface. This project used near-infrared (NIR) spectroscopy to examine this process in laboratory analogs. Samples of nitrogen doped to appropriate low concentrations with methane and/or carbon monoxide were deposited at 50 K or below, and the resulting films irradiated with varied doses of 1 MeV protons. The formation of ethane, and other products, was observed at radiation dosages consistent with levels experienced at the planet=s surface. However, neither the intensity nor bandwidths of the spectroscopic signals compared very well with the NIR telescopic data. These facts lend some support to a model suggesting two different terrains on the planet, one with low methane concentration, and another with much higher levels. Irradiation of the latter might account for the ethane signals observable from Earth. The laboratory irradiation experiments also resulted in the formation of a residue, stable at high temperatures, consistent with models of organic polymer formation on icy bodies in the outer solar system. Some attempts at determining the composition of the residue were also performed. Abstract:An understanding of the formation of larger molecules in the outer solar system, by radiation induced processing of more primitive constituents, has implications relating to the evolution of the solar system. Organic residues formed by cosmic ray irradiation on cosmic ices may also have some exobiological significance, directly relating to the process from which life began on Earth. Since Pluto is one of the most primitive, and well-pres...

show abstract

The organic aerosols of Titan

Cited by 122 publications

References 23 publications

Optical properties of poly-HCN and their astronomical applications

Optical properties of poly-HCN and their astronomical applications

Tholins and their relevance for astrophysical issues

Function of Maximal Microvessel Density in Breast Tumor Metastasis

Contact Info

Product

Resources

About